Photoresist compositions

ABSTRACT

The invention provides photoresist compositions comprising a resin binder having acid labile blocking groups requiring an activation energy in excess of 20 Kcal/mol. for deblocking, a photoacid generator capable of generating a halogenated sulfonic acid upon photolysis and optionally, a base additive. It has found that linewidth variation is substantially reduced when using the halogenated sulfonic aced generator in a process involving a high temperature post exposure bake.

This application is a continuation of application(s) application Ser.No. 8/921,985 filed on Aug. 28, 1997, now U.S. Pat. No. 6,037,107.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to photoresist compositions particularly suitablefor DUV exposure. The resists are capable of forming uniform features ofsubmicron dimension across the full width of a semiconductor wafer. Moreparticularly, the invention provides a photoresist film where linewidthvariation as a function of high temperature post exposure bake isminimized.

2. Background

Photoresists are photosensitive films for transfer of an image to asubstrate. These resists form negative or positive images. After coatinga photoresist coating composition onto a substrate, the coating isexposed through a patterned photomask to a source of activating energysuch as ultraviolet light to form a latent image in the coating. Thephotomask has areas both opaque and transparent to activating radiationthat define a desired image to be transferred to the underlyingsubstrate. A relief image is provided by development of the latent imagepattern in the resist coating.

The use of photoresists is generally described, for example, byDeForest, Photoresist Materials and Processes, McGraw Hill Book Company,New York (1975), and by Moreau, Semiconductor Lithography, Principals,Practices and Materials, Plenum Press, New York (1988).

Recent developments in photoresist imaging involve formulation ofphotoresists imaged by exposure of coatings to deep ultraviolet (DUV)radiation. As is known by those in the art, DLUV refers to exposureradiation having a wavelength in the range of about 350 nm or less, moretypically in the range of about 300 nm or less and most often, 248 nm.Photoresists imaged by DUV exposure offer the advantage of providingpatterns of reduced feature size compared to photoresists imaged byexposure to radiation of longer wavelength.

“Chemically amplified” photoresist compositions have been developed thatare especially suitable for DUV imaging. Chemically amplifiedphotoresists may be negative or positive-acting and rely on manycrosslinking events (in the case of a negative-acting resist) ordeprotection reactions (in the case of a positive-acting resist), eachcatalyzed by photogenerated acid or base. In the case of the positivechemically amplified resist, certain cationic photoinitiators capable ofyielding a photogenerated acid have been used to induce cleavage ofcertain “blocking” groups pendant from a photoresist binder, or cleavageof certain groups that comprise a certain photoresist binder backbone.See, for example, U.S. Pat. Nos. 4,491,628; 4,810,613; 4,883,740;4,968,581; 5,075,199; 5,258,257; 5,362,600; 5,492,273; 5,558,971 andCanadian Patent Application No. 2,001,384, each incorporated herein byreference for its disclosure of DUV positive working chemicallyamplified photoresist formulations and blocking groups. Upon exposure ofa photoresist coating and a post exposure bake, selected cleavage of theblocking group results in formation of a polar functional group, e.g.,hydroxyl, carboxyl or imide. The generation of a polar functional groupprovides differential solubility characteristics between exposed andunexposed areas of the resist coating.

The above patents illustrate a variety of blocking groups that may beutilized for positive working chemically amplified photoresists. Eachblocking group requires a given quantity of energy to effect deblocking.The required energy is known in the art as the activation energy. Ameans to determine activation energy is described by Wallraff et al.,Kinetics of Chemically Amplified Resists, Photopolymers Principles,Processes, and Materials, Tenth International Technical Conference, pp.11-17, Oct. 31-Nov. 2, 1994, Society of Plastic Engineers, Inc. and byWallraff et al., J Vac. Sci Technol., 1995, 12 (6) 3857. Activationenergy is expressed in units of Kcal/mol. Blocking groups having greateractivation energy for deblocking require more severe conditions toeffect deblocking. Means for overcoming greater activation energyinclude use of a stronger photogenerated acid and/or higher baketemperatures.

Many different blocking groups are disclosed in the above identifiedpatents. For example, in U.S. Pat. No. 5,558,971, the blocking group isan acetal or ketal group of the formula “—OCR¹R²OR³” where R¹ and R² areindependently a hydrogen atom, a straight-chain, branched or cyclicalkyl group having 1-6 carbon atoms, a straight-chain or branchedhaloalkyl group having 1-6 carbon atoms, or a phenyl group, providedthat R¹ and R² are not hydrogen at the same time, or R¹ and R² maycombine to form a methylene chain having 2-5 carbon atoms, and R³ is astraight chain, branched or cyclic alkyl group having 1-10 carbon atoms,a straight-chain, branched or cyclic haloalkyl group having 1-6 carbonatoms, an acetyl group or an aralkyl group.

The acetal or ketal group as represented by the above formula isdeblocked at a relatively low activation energy, typically from about 10to 20 Kcal/mol. To effect deblocking, a relatively weak photogeneratedacid and/or a relatively low temperature post exposure bake or both maybe used to effect the deblocking reaction. Though this is desirable forprocessing of the photoresist coating, a low activation energyformulation suffers certain disadvantages. For example, deblocking ofthe blocking group may randomly occur during storage of the photoresistin its container. A decreased number of blocking groups on the polymerbackbone would likely result in an unpredictable change in resistphotospeed upon imaging.

To avoid storage instability, certain vendors of chemically amplifiedresists have used blocking groups that require a greater activationenergy. For example, in U.S. Pat. No. 5,362,600, the blocking groupconforms to the formula —CR⁴R⁵C(═O)OR⁶ where each of R⁴ and R⁵ isindependently selected from the hydrogen, an electron withdrawing groupsuch as halogen, lower alkyl having 1 to about 10 carbon atoms, andsubstituted lower alkyl having 1 to about 10 carbon atoms; and R⁶ is asubstituted or unsubstituted lower alkyl having from 1 to about 10carbon atoms, substituted or unsubstituted aryl having from 1 to about10 carbon atoms, and substituted or unsubstituted benzyl having 7 toabout 10 carbon atoms. The substituents can be, for example, one or moreof halogen, lower alkyl, lower alkoxy, aryl or benzyl. R⁴ and R⁵desirably are each hydrogen. If R⁴ and/or R⁵ are halogen or otherelectron-withdrawing group, upon acidic cleavage of the acetate group, ahighly polar group is formed providing enhanced solubility differentialbetween exposed and unexposed regions of the photoresist coating. Thedifluoro group. (i.e., R⁴ and R⁵ are both fluoro) is especially suitableand provides extremely high dissolution differential between exposed andunexposed regions with only modest levels of substitution of hydroxygroups on the polymer binder.

For the high energy blocking groups described above, an activationenergy of at least 20 Kcal/mole is required and typically, the requiredactivation energy is within the range of from 25 to 40 Kcal/mole. Toenable deblocking to occur, it is necessary to use one or both of aphotoacid generator capable of liberating a strong acid and/or a hightemperature post exposure bake, typically a temperature in excess of120° C. and preferably, a temperature of from about 130° C. to 150° C.or higher.

For reasons set forth above, those photoresists using blocking groupsrequiring high activation energy are generally subjected to one andoften two high temperature baking steps. In practice, it has been foundthat with high temperature baking, minor variations in the baketemperature, i.e., variations of ±1° C., across the width of thephotoresist coating can lead to significant variation in linewidthacross the developed coating and that this variation increases withincreased bake temperature. This sensitivity is referred to in the artas PEB sensitivity which is defined as changes in linewidth at a fixedexposure dose on wafers that are post-exposure baked at increasingtemperatures. The measured linewidth on each wafer is plotted againstthe PEB temperature and the PEB sensitivity in nm/° C. is the slope ofthe line. PEB sensitivity may be as much as 5% per degree Celsius. It isknown that it is difficult to maintain a uniform temperature across thefull width of the resist coating—i.e., across the full width of a wafercoated with photoresist which may be 8 or more inches in diameter.

Linewidth variation is unacceptable for most commercial applications.Therefore, it would be desirable to have chemically amplifiedphotoresist compositions capable of providing highly resolved fine lineimages, including images of submicron and sub half-micron dimension,which are PEB insensitive. It would be particularly desirable to havesuch a chemically amplified photoresist where variation in linewidth asa function of post exposure bake temperature is reduced or eliminated.

SUMMARY OF THE INVENTION

The present invention provides a chemically amplified photoresistcomposition comprising a resin binder having acid labile blocking groupsrequiring an activation energy in excess of 20 Kcal/mole, a photoacidgenerator capable of generating a strong halogenated sulfonic acid uponphotolysis, and optionally a base additive. It has been found that PEBsensitivity as a consequence of a high temperature bake is substantiallyreduced when using the halogenated sulfonic acid generator and further,the base additive also contributes to a reduction in the PEBsensitivity. Accordingly, the photoresists of the invention providephotoresist coating composition capable of forming highly resolvedrelief images of submicron dimension with vertical or essentiallyvertical sidewalls, uniformly imaged across the full width of a waferover which the photoresist is coated, regardless of the temperaturedifferential across the surface of the resist coating during the bakestep.

The photoacid generator used in the formulation of the invention is onethat yields a strong halogenated sulfonic acid upon photolysis,preferably one having a pK_(a) no greater than 0, and more preferably, apK_(a) of between −5.0 and −15.0. Preferred photoactive generators aresulfonate salts of compounds containing a strong halogen electronwithdrawing group such as the fluorine atom. Suitable bases optionallyused in combination with the acid generator are those preferably havinga pK_(a) of at least 9.0 and more preferably, a pK_(a) between 11.0 and15.0. Desirably, the strong base is a quaternary ammonium hydroxide.

The invention also provides methods for forming relief images using thephotoresists of the invention and articles of manufacture comprisingsubstrates such as a microelectronic wafer or a flat panel displaysubstrate coated with the photoresists invention. Other aspects of theinvention are disclosed infra.

DETAILED DESCRIPTION OF THE INVENTION

The photoresists of the invention comprise a resin binder, a photoacidgenerator that liberates a halogenated sulfonic acid upon photolysis andoptionally, a base. The photoresist is used in a process comprising thesteps of coating the same onto a substrate, imaging to DUV irradiationand post exposure baking the resist coating at a temperature in excessof 120° C. and preferably in excess of 130° C.

The resin binder component of the photoresist desirably contains phenolunits substituted with acid labile groups which may be pendant from theresin backbone. The resin is used in an amount sufficient to render anexposed coating of the resist developable such as with an aqueousalkaline solution. Exemplary phenolic resins containing acid labilegroups are disclosed in the above mentioned patents such as U.S. Pat.No. 4,491,628 to Ito as well as in U.S. Pat. No. 5,258,257 to Sinta etal, and U.S. Pat. No. 5,492,793 to Ito, each, incorporated herein byreference.

Typical resin binders comprise polymers such as novolak resins andpolyvinylphenol resins. A preferred polymer suitable for purposes of theinvention comprises units of a structure selected from the groupconsisting of

where unit (1) represents a phenolic unit and unit (2) represents acyclic alcohol unit; Z is an alkylene bridge having from 1 to 3 carbonatoms; A is a substituent on the aromatic ring replacing hydrogen suchas lower alkyl having from 1 to 3 carbon atoms, halo such as fluoro,chloro or bromo, alkoxy having from 1 to 3 carbon atoms, hydroxyl,nitro, amino, etc.; B is a substituent such as hydrogen, lower alkylhaving from 1 to 3 carbon atoms, halo such as fluoro, chloro or bromo,alkoxy having from 1 to 3 carbon atoms, hydroxyl, nitro, amino, etc.,provided that at least 3 of said B substituents are hydrogen; a is anumber varying from 0 to 3; b is an integer varying between 6 and 10;and x is the mole fraction of units (1) in the polymer. The percentageof cyclic alcohol units preferably is not so high as to preventdevelopment of an exposed film in a polar developer. The polymertherefore should have a major portion of phenolic units and a minorportion of cyclic alcohol units, i.e., less than about 50 mole percentof cyclic alcohol units. However, it has been found that thetransparency of said photoresist composition increases with increasingconcentration of cyclic alcohol units and for this reason, in certaincases, it may be desirable to employ a polymer having a major portion ofcyclic alcohol units and a minor portion of phenolic units. This can heachieved by using suitable blocking groups which upon acid catalyzedhydrolysis provide polar functional groups rendering exposed regionshighly soluble in polar developer solutions.

An additional suitable class of resins comprises a copolymer ofhydroxystyrene and an acrylate, methacrylate or a mixture of the two.The hydroxystyrene component provides base solubility to the resistcomposition. This component is suitably the para- or meta- isomer andcan be substituted with various substituents that do not interfere withlithography such as halogen, methoxy or lower alkyl, e.g. methyl orethyl. α-Methyl-hydroxy-styrene monomer can also be incorporated intothe polymer. The ester group of the acrylate or the methacrylate is anacid labile group which inhibits the dissolution of the polymer inalkaline developer and provides acid sensitivity to the polymer.Polymers of this description may be represented by the followingstructural formula:

where x′ represents the mole fraction of the hydroxystyrene units and y′represents the mole fraction of the acrylate units, the hydroxyl groupon the hydroxystyrene may be present at either the ortho, meta or parapositions throughout the copolymer, and R⁷ is substituted orunsubstituted alkyl having 1 to about 18 carbon atoms, more typically 1to about 8 carbon atoms. Tert-butyl is a generally preferred R⁷ group.An R⁷ group is desirably substituted by e.g. one or more halogen atoms(particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. The units x′and y′ may be regularly alternating in the copolymer, or may be randomlyinterspersed through the polymer. Preferably, x′ varies between 0.5 and0.95 and y′ varies between 0.05 and 0.5.

A preferred class of resins within the above generic formula may berepresented as follows:

where x′, y′, and R⁷ are as defined above and R′ and R″ areindependently halogen, substituted or unsubstituted alkyl having from 1to 8 carbon atoms, substituted or unsubstituted alkoxy having 1 to 8carbon atoms, substituted or unsubstituted alkenyl having 2 to 8 carbonatoms, substituted or unsubstituted alkylthio having 1 to 8 carbonatoms, cyano, nitro, etc., and m and p are individually 0 to 5. Polymersconforming to the above formula are disclosed in U.S. Pat. No. 5,861,231and incorporated herein by reference.

A particularly preferred copolymer of the invention corresponds to thefollowing Formula I:

wherein R¹¹ of units 1) is substituted or unsubstituted alkyl preferablyhaving 1 to about 10 carbon atoms, more typically 1 to about 6 carbons.Branched alkyl such as tert-butyl are generally preferred R¹¹ groups.Also, the polymer may comprise a mixture of different R¹¹ groups, e.g.,by using a variety of acrylate monomers during the polymer synthesis.

R¹ groups of units 2) of Formula I each independently may be e.g.halogen (particularly F, Cl and Br), substituted or unsubstituted alkylpreferably having 1 to about 8 carbons, substituted or unsubstitutedalkoxy preferably having 1 to about 8 carbon atoms, substituted orunsubstituted alkenyl preferably having 2 to about 8 carbon atoms,substituted or unsubstituted alkynyl preferably having 2 to about 8carbons, substituted or unsubstituted alkylthio preferably having 1 toabout 8 carbons, cyano, nitro, etc.; and m is an integer of from 0(where the phenyl ring is fully hydrogen-substituted) to 5, andpreferably is 0, 1 or 2. Also, two R¹ groups on adjacent carbons may betaken together to form (with ring carbons to which they are attached)one, two or more fused aromatic or alicyclic rings having from 4 toabout 8 ring members per ring. For example, two R¹ groups can be takentogether to form (together with the depicted phenyl) a naphthyl oracenaphthyl ring. As with units 1), the polymer may comprise a mixtureof different units 2) with differing R¹ groups or no R¹ groups (i.e.m=0) by using a variety of substituted or unsubstituted vinylphenylmonomers during the polymer synthesis.

R² groups of units 3) of Formula I each independently may be e.g.halogen (particularly F, Cl and Br), substituted or unsubstituted alkylpreferably having 1 to about 8 carbons, substituted or unsubstitutedalkoxy preferably having 1 to about 8 carbon atoms, substituted orunsubstituted alkenyl preferably having 2 to about 8 carbon atoms,substituted or unsubstituted sulfonyl preferably having 1 to about toabout 8 carbon atoms such as mesyl (CH₃ SO₂ O—), substituted orunsubstituted alkyl esters such as those represented by R¹²COO— whereR¹² is preferably an alkyl group preferably having 1 to about 10 carbonatoms, substituted or unsubstituted alkynyl preferably having 2 to about8 carbons, substituted or unsubstituted alkylthio preferably having 1 toabout 8 carbons, cyano, nitro, etc.; and p is an integer of from 0(where the phenyl ring has a single hydroxy substituent) to 4, andpreferably is 0, 1 or 2. Also, two R² groups on adjacent carbons may betaken together to form (with ring carbons to which they are attached)one, two or more fused aromatic or alicyclic rings having from 4 toabout 8 ring members per ring. For example, two R² groups can be takentogether to form (together with the phenol depicted in Formula I) anaphthyl or acenaphthyl ring. As with units 1), the polymer may comprisea mixture of different units 3) with differing R² groups or no R² groups(i.e. p=0) by using a variety of substituted or unsubstitutedvinylphenyl monomers during the polymer synthesis. As shown in Formula Iabove, the hydroxyl group of units 3) may be either at the ortho, metaor para positions throughout the copolymer. Para or meta substitution isgenerally preferred.

Each R³, R⁴ and R⁵ substituents independently may be hydrogen orsubstituted or unsubstituted alkyl preferably having 1 to about 8 carbonatoms, more typically 1 to about 6 carbons, or more preferably 1 toabout 3 carbons.

The above-mentioned substituted groups (i.e. substituted groups R¹¹ andR¹ through R⁵) may be substituted at one or more available positions byone or more suitable groups such as halogen (particularly F, Cl or Br);C₁₋₈ alkyl; C₁₋₈ alkoxy; C₂₋₈ alkenyl; C₂₋₈ alkynyl; aryl such asphenyl; alkanoyl such as a C₁₋₆ alkanoyl of acyl and the like; etc.Typically a substituted moiety is substituted at one, two or threeavailable positions.

In the above Formula I, x, y and z are the mole fractions or percents ofunits 3), 2) and 1) respectively in the copolymer. These mole fractionsmay suitably vary over rather wide values, e.g., x may be suitably fromabout 10 to 90 percent, more preferably about 20 to 90 percent; y may besuitably from about 1 to 75 percent, more preferably about 2 to 60percent; and z may be 1 to 75 percent, more preferably about 2 to 60percent.

Preferred copolymers include those where the only polymer unitscorrespond to the general structures of units 1), 2) and 3) above andthe sum of the mole percents x, y and z equals one hundred. However,preferred polymers also may comprise additional units wherein the sum ofx, y and z would be less than one hundred, although preferably thoseunits 1), 2) and 3) would still constitute a major portion of thecopolymer, e.g. where the sum of x, y and z would be at least about 50percent (i.e. at least 50 molar percent of the polymer consists of units1), 2) and 3)), more preferably the sum of x, y and z is at least 70percent, and still more preferably the sum of x, y and z is at least 80or 90 percent.

The above described polymers can be readily formed. For example, forresins of the above formula, vinyl phenols and a substituted orunsubstituted alkyl acrylate such as t-butylacrylate and the like may becondensed under free radical conditions as known in the art. Thesubstituted ester moiety, i.e., R⁷—O—C(═O)—, moiety of the acrylateunits serves as the acid labile groups of the resin and will undergophotoacid induced cleavage upon exposure of a coating of a photoresistcontaining the resin to DUV irradiation. Preferably the copolymer willhave a M_(w) of from about 2,000 to about 50,000, more preferably about5,000 to about 30,000 with a molecular weight distribution of about 3 orless, more preferably a molecular weight distribution of about 2 orless. Desirably, the terpolymer contains the hydroxystyrene in the rangeof 50 to 90 mol % depending on the desired dissolution rate/sensitivity.The terpolymer has a high glass transition temperature of about 130° C.to about 170° C. The terpolymer also has a high acid sensitivity. Theacid labile ester groups of the terpolymer are surprisingly thermallystable in the presence of the phenolic hydroxy groups up to atemperature of about 180° C. This enables high temperature pre- and postexposure baking of a film of the composition which results insubstantially improved lithographic performance. Additional detailsrelating to the formation of such polymerscan be found in U.S. Pat. No.5,492,793 and in the above cited copending patent application.

In addition to the resins described above, non-phenolic resins, e.g. acopolymer of an alkyl acrylate such as t-butylacrylate ort-butylmethacrylate and a vinyl alicyclic monomer such as a vinylnorbornyl or vinyl cyclohexanol compound may be prepared by such freeradical polymerization or other known procedures and used as a binder inthe photoresists described herein.

At least a portion of the available hydroxyl groups on any of the abovedescribed polymer binders are bonded to an acid labile blocking group.In accordance with the invention, suitable blocking groups are thosethat deblock at an activation energy of at least 20 Kcal/mole and which,upon photocleavage, provide a group that is at least as polar ashydroxyl.

Using vinylic polymers for purposes of illustration, the acid labileblocking groups are generally used in accordance with the followingscheme in which a preferred polymer binder is condensed with a compoundthat comprises an acid labile group R and a suitable leaving group (L).

In the scheme shown described above, unit (1) represents a phenolic unitand unit (2) represents a cyclic alcohol unit: A, B, a, b and x are asdefined above, R′ is an acid labile blocking group; P is a polar groupformed by acidic cleavage of the acid labile blocking group R; and y isthe mole fraction of units substituted with an acid labile group. Themole fraction represented by y may differ between aromatic units andcyclic alcohol units. Upon exposure, the photogenerated acid cleaves theacid labile group which is converted from a dissolution inhibiting groupto a base soluble organic group thereby enabling image development ofthe composition.

Regardless of the resin used as the photoresist binder, it issubstituted with an acid labile group that yields a suitable leavinggroup at an activation energy of 20 Kcal/mol or greater. For example, toprovide acid labile acetic acid groups pendant to the resin binderbackbone, the preformed resin binder may be condensed with a compound ofthe formula L—CR⁸R⁹C(═O)—OR¹⁰, where L is a leaving group such asbromide or chloride as described above, R⁸ and R⁹ are, eachindependently hydrogen, an electron withdrawing group such as halogen(particularly F, Cl or Br), or substituted or unsubstituted C₁₋₁₀ alkyl;and R¹⁰ is substituted or unsubstituted C₁₋₁₀ alkyl or substituted orunsubstituted aryl such as phenyl or aralkyl such as benzyl. Thecondensation provides the —CR⁸R⁹C(═O)—O—R¹⁰ groups pendant to the resinbinder backbone and grafted onto the resin's available hydroxyl groups.Photoacid degradation of these groups during exposure and/orpost-exposure heating provides the polar acetic acid ether moietypendant to the resin binder backbone. Other acid labile groups may alsobe employed, e.g. oxycarbonyl groups such as those of the formula—C(═O)OR⁶ where R⁶ is as defined above and preferably is t-butyl orbenzyl. See U.S. Pat. No. 5,258,257 to Sinta et al. incorporated hereinby reference for a discussion of acid labile groups and preparation anduse of resist resin binders comprising acid labile groups.

The photoresist compositions of the invention also contain a photoacidgenerator capable of generating a strong acid upon exposure to deep UVradiation. The photoacid generator is one that liberates a sulfonic acidhaving a strong electron withdrawing group. The function of the electronwithdrawing group is to increase the strength of the photogeneratedacid. The sulfonic acid has a pK_(a) of 0 or less and preferably apK_(a) within a range of −5 to −15 or less. The photoacid generator issuitably employed in an amount sufficient to generate a latent image ina coating layer of the resist upon exposure to activating radiation.

In accordance with the invention, the photoacid generator is one capableof generating an acid of the formula:

X_(a)RSO₃H

where X_(a)R is an organic radical substituted with strong electronwithdrawing groups X. R may be alkyl having from 1 to 18 carbon atoms,aryl such as phenyl, benzyl, naphthyl, etc. Strong electron withdrawinggroups that may be substituted onto R are exemplified by halo, nitro,cyano; etc., preferably fluoro. The letter a represents the number ofstrong electron withdrawing groups substituted onto R and is a wholenumber preferably equal to 1 to 18. Preferred strong acids conforming tothe above formula are perfluorooctane sulfonic acid and2-trifluoromethylbenzene sulfonic acid. Representative examples ofcompounds capable of generating acids conforming to the abovegeneralized formula are given below where nomenclature and substituentidentification used in the text is derived from an identified referencesource and where, from time to time, the (X_(a)RSO₃)⁻ radical issubstituted onto the exemplified material.

One class of suitable photoacid generators is disclosed in U.S. Pat. No.5,558,976. Representative examples of these photoacid generatorsinclude:

where R⁷ is a straight-chain, branched or cyclic alkyl group having from1 to 10 carbon atoms and Z is a sulfonyl group or a carbonyl group:

where R is as defined above; and

where R²² is hydrogen, hydroxyl or a group represented by the formulaX_(a)RSO₂O— where X_(a)R is as defined above, and R²³ is a straight orbranched alkyl group having from 1 to 5 carbon atoms or a grouprepresented by the formula:

where R²⁴ and R³⁰ are independently a hydrogen atom, a halogen atom, astraight chain or branched alkyl group having 1-5 carbon atoms, astraight chain or branched alkoxy group having 1-5 carbon atoms, or agroup of the formula:

where R²⁵ is a straight chain or branched alkyl group having 1-4 carbonatoms, a phenyl group, a substituted phenyl group or an aralkyl group;R²⁶ is a hydrogen atom, a halogen atom or a straight-chain, branched orcyclic alkyl group having 1-6 carbon atoms; R²⁷ is a straight chain orbranched perfluoroalkyl group having 1-8 carbonatoms, a straight chain,branched or cyclic alkyl group having 1-8 carbon atoms, a 1-naphthylgroup, a 2-naphthyl group, a 10-camphor group, a phenyl group, a tolylgroup, a 2,5-dichlorophenyl group, a 1,3,4-trichlorophenyl group or atrifluoromethylphenyl group.

Nitrobenzyl based compounds are disclosed in EPO published applicationNo. EP 0 717 319 A1 incorporated herein by reference. Such compounds maybe defined by the following general formula:

where each R₁, R₂ and R₃ are individually selected from the groupconsisting of hydrogen and lower alkyl group having from 1-4 carbonatoms; and R₄ and R₅ are individually selected from the group consistingof CF₃ and NO₂ with the proviso that R₄ and R₅ cannot both be CF₃; andRX_(a) is as defined above.

N-sulfonyloxyimide PAGs may also be used in the compositions of theinvention and are as disclosed in World application WO94/10608incorporated herein by reference. These materials conform to theformula:

where the carbon atoms form a two carbon structure having a single,double or aromatic bond, or, alternatively, wherein they form a threecarbon structure, that is, where the imide ring is a fives member or sixmember ring; X and Y (1) form a cyclic or polycyclic ring which maycontain one or more hetero atoms, or (2) form a fused aromatic ring, or(3) may be independently hydrogen, alkyl or aryl, or (4) may be attachedto another sulfonyloxyimide containing residue, or (5) may be attachedto a polymer chain or backbone, or alternatively, form

where R₁ is selected from the group consisting of H, acetyl, acetamido,alkyl having 1 to 4 carbons where m=1 to 3, NO₂ where m=1 to 2, F wherem=1 to 5, Cl where m=1 to 2, CF₃ where m=1 to 2, and OCH₃ where m=1 to2, and where m may otherwise be from 1 to 5, and combinations thereof;and where X and Y (1) form a cyclic or polycyclic ring which may containone or more hetero atoms, (2) form a fused aromatic ring, (3) may beindependently H, alkyl or aryl, (4) may be attached to anothersulfonyloxyimide containing residue, or (5) may be attached to apolymeric chain or backbone.

Iodonium salt photoacid generators are disclosed in published Europeanapplication 0 708 368 A1 and represent another preferred acid generator.Such salts are represented by the following formula:

where Ar¹ and Ar² each independently represents a substituted orunsubstituted aryl group. A preferred example of the aryl group includesa C₆₋₁₄ monocyclic or a condensed ring aryl group. Preferred examples ofthe substituent on the aryl group include an alkyl group, a haloalkylgroup, a cycloalkyl group, an aryl group, an alkoxy group, a nitrogroup, a carboxyl group, an alkoxycarbonyl group, a hydroxyl group,mercapto group, and a halogen atom. Sulfonium salts represent the mostpreferred embodiment of the invention and are represented by thefollowing formula:

R³, R⁴ and R⁵ each independently represents a substituted orunsubstituted alkyl group or aryl group. With regard to each of theabove formulae, preferred examples of the substituted or unsubstitutedalkyl group and aryl group include a C₆₋₁₄ aryl group, a C₁₋₅ alkylgroup, and substituted derivatives thereof. Preferred examples of thesubstituent on the alkyl group include a C₁₋₈ alkoxy group, a C₁₋₈ alkylgroup, nitro group, carboxyl group, hydroxyl group, and a halogen atom.Preferred examples of the substituent on the aryl group include a C₁₋₈alkoxy group, carboxyl group, an alkoxycarbonyl group, a C₁₋₈ haloalkylgroup, a C₅₋₈ cycloalkyl group and a C₁₋₈ alkylthio group. Two of R³, R⁴and R⁵ and Ar¹ and Ar² may be connected to each other via its singlebond or a substituent.

Disulfone derivatives are also suitable for the formulations of thisinvention and are disclosed in published European application 0 708 368A1. Such materials may be represented by the following formulae:

Ar³—SO₂—SO₂—RX_(a)

wherein RX_(a) is as defined above and Ar³ represents a substituted orunsubstituted aryl group. A preferred example of the aryl group includesa C₆₋₁₄ monocyclic or condensed-ring aryl group. Preferred examples ofthe substituent on the aryl group include an alkyl group, a haloalkylgroup, a cycloalkyl group, an aryl group, an alkoxy group, nitro group,carboxyl group, an alkoxycarbonyl group, hydroxyl group, mercapto group,and halogen.

Of the photoacid generators contemplated for use in the photoresists ofthe invention, most preferred are di-(4-t-butylphenyl) iodoniumperfluorooctane sulfonate and di-(4-t-butylphenyl) iodonium2-trifluoromethyl benzene sulfonate.

The photoresist composition of the invention preferably contains astrong base having a pK_(a) of at least 9 and preferably a pK_(a) withinthe range of from about 11 to 15. A preferred base for the photoresistof the invention would conform to the formula N(R′)₄A where each R′ isindependently substituted or unsubstituted alkyl preferably having from1 to about 12 carbon atoms, more typically 1 to about 8 carbon atoms, ora substituted or unsubstituted aryl such as a C₆₋₁₀ aryl, e.g., phenyl,naphthyl and the like, A is a counter anion of a halide, a substitutedor unsubstituted hydroxyalkanoyl preferably having 1 to about 18 carbonatoms (i.e. a group substituted by hydroxy and carbonyl such as lactate—CH₃CH(OH)C(═O)0⁻), substituted or unsubstituted sulfonate including aC₆₋₁₈ aryl or C₁₋₁₂ alkyl sulfonate. The term hydroxyalkanoyl as usedherein refers to an alkanoyl group having one or more hydroxy moieties(typically 1, 2, 3 or 4 hydroxy moieties) on one or more carbons of thealkanoyl group. Exemplary sulfonate A groups include mesylate, triflate,tosylate, etc. Substituted A groups may be suitably substituted by oneor more groups such as halo particularly fluoro, chloro and bromo,cyano, nitro, C₁₋₁₂ alkyl, C₂₋₁₂ alkyl, C₂₋₁₂ alkenyl, C₁₋₁₂ alkoxy,C₁₋₁₂ alkanoyl including acyl, etc. Additional amines can be found inU.S. Pat. No.5,498,506 and SPIE, 2438, 563, 1995. Examples of suitableamines include ammonium sulfonate salts such as piperidiniump-toluenesulfonate and dicylohexylammonium p-tolunesulfonate; alkylamines such as tripropylamine and dodecylamine; aryl amines such asdiphenylamine, triphenylamine, aminophenol,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane, etc.

The base can be added to the photoresist composition in a relativelysmall amount, for example, from about 0.01 to 5 percent by weight of thepolymer and more preferably, from 0. 05 to 1 percent by weight.

An optional component of the photoresist composition of the invention isa dye. Preferred dyes enhance resolution of the patterned resist image,typically by reducing reflections and the effects thereof (e.g.notching) caused by the exposure radiation. Preferred dyes includesubstituted and unsubstituted phenothiazine, phenoxazine, anthracene andanthrarobin compounds. Preferred substituents of substitutedphenothiazine, phenoxazine, anthracene and anthrarobin include e.g.halogen, C₁₋₁₂ alkyl, C₁₋₂ alkoxy, C₂₋₁₂ alkenyl, C₁₋₁₂ alkanoyl such asacetyl, aryl such as phenyl, etc. Copolymers of such compounds also maybe used as a dye, e.g., an anthracene acrylate polymer or copolymer. Acurcumin dye also may be used for some applications. In addition toreducing reflections in deep U.V. exposures, use of a dye may expand thespectral response of the compositions of invention.

Photoresists of the invention also may contain other optional materials.For example, other optional additives include anti-striation agents,plasticizers, speed enhancers, etc. Such optional additives typicallywill be present in minor concentration in a photoresist compositionexcept for fillers and dyes which may be present in relatively largeconcentrations such as, e.g., in amounts of from about 5 to 30 percentby weight of the total weight of a resist's dry components.

The compositions of the invention can be readily prepared by thoseskilled in the art. For example, a photoresist composition of theinvention can be prepared by dissolving the components of thephotoresist in a suitable solvent such as, for example, a glycol etherexemplified by 2-methoxyethyl ether (diglyme), ethylene glycolmonomethyl ether, propylene glycol monomethyl ether; a Cellosolve estersuch as Cellosolve acetate, propylene glycolmonomethyl ether, methylethyl ketone, ethyl lactate, etc. Typically, the solids content of thecomposition varies between about 5 and 35 percent by weight of the totalweight of the photoresist composition. The resin binder and PAGcomponents should be present in amounts sufficient to provide a filmcoating layer and formation of good quality latent and relief images.See the examples which follow for exemplary preferred amounts of resistcomponents.

The compositions of the invention are used in accordance with generallyknown procedures. The liquid coating compositions of the invention areapplied to a substrate such as a semiconductor by spinning, dipping,roller coating, slot coating or other conventional coating technique.When spin coating, the solids content of the coating solution may beadjusted to provide a desired film thickness based upon the specificspinning equipment utilized, the viscosity of the solution; the speed ofthe spinner and the amount of time allowed for spinning.

The resist compositions of the invention are applied to substratesconventionally used in processes involving coating with photoresists.For example, the composition may be applied over silicon or silicondioxide wafers for the production of microprocessors and otherintegrated circuit components. Aluminum-aluminum oxide, galliumarsenide, ceramic, quartz or copper substrates also may be employed.Substrates used for liquid crystal display and other flat panel displayapplications are also suitably employed, e.g. glass substrates, indiumtin oxide coated substrates and the like.

Following coating of the photoresist onto a surface, it is dried byheating to remove the solvent until preferably the photoresist coatingis tack free. Thereafter, it is imaged through a mask in conventionalmanner. The exposure is sufficient to effectively activate thephotoactive component of the photoresist system—i.e., generatesufficient acid to produce a patterned image in the resist coating layerfollowing post exposure bake, and more specifically, the exposure energytypically ranges from about 1 to 300 mJ/cm², dependent upon the exposuretool and the components of the photoresist composition.

Coating layers of the resist composition of the invention are preferablyphotoactivated by an exposure wavelength in the deep U.V. range i.e.,350 nm or less, more typically in the range of about 300 nm or less,typically about 150 to 300 or 350 nm. A particularly preferred exposurewavelength is about 248 nm.

Following exposure, the film layer of the composition is preferablybaked at temperatures ranging from about 120° C. to about 160° C.Thereafter, the film is developed. The exposed resist film is renderedpositive working by employing a polar developer, preferably an aqueousbased developer such as an inorganic alkali exemplified by sodiumhydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate,sodium silicate, sodium metasilicate; quaternary ammonium hydroxidesolutions such as a tetra-alkyl ammonium hydroxide solution; variousamine solutions such as ethyl amine, n-propyl amine, diethyl amine,di-n-propyl amine, triethyl amine, or methyldiethyl amine; alcoholamines such as diethanol amine or triethanol amine; cyclic amines suchas pyrrole, pyridine, etc. In general, development is in accordance withart recognized procedures.

Following development of the photoresist coating over the substrate, thedeveloped substrate may be selectively processed on those areas bared ofresist, for example by chemically etching or plating substrate areasbared of resist in accordance with procedures known in the art. For themanufacture of microelectronic substrates, e.g., the manufacture ofsilicon dioxide wafers, suitable etchants include a plasma gas etch(e.g. an oxygen plasma etch) and a hydrofluoric acid etching solution.The compositions of the invention are highly resistant to such etchantsthereby enabling manufacture of highly resolved features, includinglines with submicron widths. After such processing, resist may beremoved from the processed substrate using known stripping procedures.

The following examples illustrate the invention.

SYNTHESIS EXAMPLES Example 1 Preparation of Di-(4-t-Butylphenyl)iodonium2-trifluoromethylbenzenesulfonate

Part A: Preparation of 2-Trifluoromethybenzenesulfonic acid

A 1 L 3 neck flask was charged with 2-trifluoromethybenzenesulfonylchloride (134.55 g, 0.55 mol) and water (320 mL). The reaction flask wasfitted with a condenser, an overhead stirrer and a nitrogen bubbler andthe biphasic reaction mixture heated at reflux for 24 h. During thistime, the sulfonyl chloride hydrolyzed to2-trifluoromethylbenzenesulfonic acid, giving a clear homogeneoussolution. The aqueous solution was concentrated under vacuum and thesolid residue further dried in vacuum at 40° C. for 24 h to give2-Trifluoromethylbenzenesulfonic acid as an off white solid.

Part B: Preparation of Di-(4-t-butylphenyl)iodonium2-trifluoromethylbenzenesulfonate

A 1 L 3 neck round bottom flask equipped was charged t-butylbenzene(134.22 g, 1.00 mol) and acetic anhydride (204.18 g, 2.00 mol). Theflask was fitted with an efficient overhead paddle stirrer and thestirrer started while potassium iodate (107.00 g, 0.50 mol) was added togive a white suspension. The reaction vessel was then equipped with athermometer and a pressure equalizing dropping funnel (125 mL) fittedwith a N₂ bubbler.

The reaction mixture was cooled to 0-5° C. in a large ice-water bath andconcentrated sulfuric acid (107.89 g, 1.10 mol) added dropwise via theaddition funnel. The addition was carried out at such a rate as tomaintain the reaction temperature in the 20-30° C. range and requiredaround 2 h. As the addition proceeded the starting white suspensionbecame orange-yellow in color and the viscosity of the reaction mixtureincreased giving a tan paste. Once the addition was over, the reactionmixture was stirred at water bath temperature (20° C.) for a further 22h. The reaction mixture was cooled to 5-10° C. and water (350 mL) wasadded dropwise over @ 30 min, maintaining the temperature below 30° C.The first @ 50 mL was added at a particularly slow rate to control theinitial exotherm, thereafter the rest of the water was essentially addedin one portion.

The resulting cloudy mixture was washed with hexane (3×75 mL) and theaqueous solution of diaryliodonium salt was returned to the reactionflask and cooled to 15-20° C. in an ice water bath.2-Trifluoromethylbenzenesulfonic acid (113.09 g, 0.50 mol) (prepared asin Part A above) was added in one portion with stirring. The resultingcloudy reaction mixture was neutralized with ammonium hydroxide (14.8N,311 mL, 4.60 mol). The amount of base used corresponds to thetheoretical amount required to neutralize all acidic species in the pot,assuming quantitative reaction. The addition of the base was carried outat such a rate as to keep the temperature below 30° C. and requiredabout 2 h. As the pH of the reaction mixture approached 6-7, a browngummy solid starts to precipitate from solution. At this point, additionof ammonium hydroxide is temporarily stopped and dichloromethane (300mL) is added to give a biphasic mixture. After stirring for 3 h, thedichloromethane layer was drained off and the aqueous layer extractedwith additional dichloromethane (2×100 mL).

The combined dichloromethane extracts was washed with dilute ammoniumhydroxide until the pH of the aqueous layer is in the 7-8 range [1×100mL, the pH of the aqueous solution was adjusted to 8-9 by addingsufficient ammonium hydroxide (14.8N) in small portions]. The organiclayer was washed with water (2×100 mL) until the pH of the aqueous phasewas around 6-7. The dichloromethane solution was concentrated on arotary evaporator under water aspirator vacuum. The resulting residue isthen purified by successive recrystallizations from ethylacetate-cyclohexane. The resulting white solid was dried at 70° C. invacuum for 36 h, to give di-(4-t-butylphenyl)iodonium2-trifluoromethylbenzenesulfonate as a white powder.

Example 2 Preparation of Di-(4-t-Butylphenyl)iodoniumPerfluorooctanesulfonate

A 1 L 3 neck round bottom flask equipped was charged t-butylbenzene(134.22 g, 1.00 mol) and acetic anhydride (204.18 g, 2.00 mol). Theflask was fitted with an efficient overhead paddle stirrer and thestirrer started while potassium iodate (107.00 g, 0.50 mol) was added togive a white suspension. The reaction vessel was then equipped with athermometer and a pressure equalizing dropping funnel (125 mL) fittedwith a N₂ bubbler. The reaction mixture was cooled to 0-5° C. in a largeice-water bath and concentrated sulfuric acid (107.89 g, 1.10 mol) addeddropwise via the addition funnel.

The addition was carried out at such a rate as to maintain the reactiontemperature in the 20-30° C. range and required around 2 h. As theaddition proceeded, the starting white suspension became orange-yellowin color and the viscosity of the reaction mixture increased giving atan paste. Once the addition was over, the reaction mixture was stirredat water bath temperature (20° C.) for a further 22 h. The reactionmixture was cooled to 5-10° C. and water (350 mL) was added dropwiseover @ 30 min, maintaining the temperature below 30° C. The first @ 300mL was added at a particularly slow rate to control the initialexotherm, thereafter the rest of the water was essentially added in oneportion.

The resulting cloudy mixture was washed with hexane (3×75 mL) and theaqueous solution of diaryliodonium salt was returned to the reactionflask and cooled to 15-20° C. in an ice water bath.Perfluorooctanesulfonic acid, potassium salt (269.11 g, 0.50 mol) wasadded in one portion with stirring. The resulting cloudy reactionmixture was neutralized with ammonium hydroxide (14.8N, 277 mL, 4.10mol). The amount of base used corresponds to the theoretical amountrequired to neutralize all acidic species in the pot, assumingquantitative reaction. The addition of the base was carried out at sucha rate as to keep the, temperature below 30° C. and required about 2 h.As the pH of the reaction mixture approached 6-7, a brown gummy solidstarts to precipitate from solution. At this point, addition of ammoniumhydroxide is temporarily stopped and dichloromethane (300 mL) is addedto give a biphasic mixture. After stirring for 3 h, the dichloromethanelayer was drained off and the aqueous layer extracted with additionaldichloromethane (2×100 mL).

The combined dichloromethane extracts was washed with dilute ammoniumhydroxide until the pH of the aqueous layer is in the 7-8 range [1×100mL, the pH of the aqueous solution was adjusted to 8-9 by addingsufficient ammonium hydroxide (14.8N) in small portions]. The organiclayer was washed with water (2×100 mL) until the pH of the aqueous phasewas round 6-7. The dichloromethane solution was concentrated on a rotaryevaporator under water aspirator vacuum. The resulting residue is thenpurified by successive recrystallizations from ethylacetate-cyclohexane. The resulting white solid was dried at 70° C. invacuum for 36 h, to give di-(4-t-butylphenyl)iodoniumperfluorooctanesulfonate as a white powder.

Example 3 Preparation: of Triphenylsulfonium Perfluorooctanesulfonate

To a suspension of perfluorooctanesulfonic acid potassium salt (10.76 g,20.0 mmol) in water (100 mL) at room temperature under nitrogen wasadded dropwise triphenylsulfonium bromide (6.87 g, 20.0 mmol) over 15min. After stirring the suspension for 30 min., dichloromethane (100 mL)was added and the biphasic mixture stirred at room temperature for 20 h.Additional dichloromethane (100 mL) was added and the layers separated.The organic layer was washed with water (3×75 mL) until the washingswere neutral (pH 7). After drying (MgSO₄), removal of the solvent invacuum gave a viscous gum which was further dried by heating at 50° C.for 24 h under vacuum. In this way, triphenylsulfoniumperfluorooctanesulfonate was isolated as a pale yellow gummy solid.

Example 4 Preparation of Triarylsulfonium Perfluorooctanesulfonate

To a suspension of perfluorooctanesulfonic acid potassium salt (24.81 g,46.1 mmol) in water (150 mL) at room temperature under nitrogen wasadded dropwise triarylsulfonium chloride (50% aqueous solution, 27.50 g)over 15 min. After stirring the suspension for 30 min., dichloromethane(75 mL) was added and the mixture stirred at room temperature for 20 h.Additional dichloromethane (225 mL) was added and the layers separated.The organic layer was washed with water (3×125 mL) until the washingswere neutral (pH 7). After drying (MgSO₄), removal of the solvent invacuum gave a viscous gum which was further dried by heating at 80-90°C. for 84 h under vacuum. In this way, triarylsulfoniumperfluorooctanesulfonate was isolated as a glassy solid.

Example 5 Preparation ofN-[(Perfluorooctanesulfonyl)oxy]-norborane-2,3-dicarboximide

A 500 mL, 3 neck flask was charged withN-hydroxy-5-norbornene-2,3-dicarboximide (22.39 g, 0.125 mol). The flaskwas fitted with a condenser, a dropping funnel, a nitrogen bubbler and amagnetic stirrer.

1,1,1,3,3,3-Hexamethyldisilazane (14.50 mL, 11.10 g, 68.75 mmol) wasadded via the dropping funnel followed by one drop ofchlorotrimethylsilane as catalyst. The suspension was brought to agentle reflux and heated there at for 3 h. The resulting solutionsolidified upon cooling to room temperature. This solid was presumed tobe the corresponding N-OTMS ether. 1,2-Dimethoxyethane (75 mL) was addedfollowed by perfluorooctanesulfonyl fluoride (37.85 mL, 69.04 g, 0.1375mol) and the resulting biphasic mixture heated to reflux. A solution oftriethylamine (3.48 mL, 2.53 g, 25.0 mmol) in 1,2-dimethoxyethane (25mL) was added to the hot solution and the mixture turned pale orange.The reaction mixture was heated at reflux for 64 h to give a darkbrown-black solution.

At this stage, TLC showed the presence of the desired product andconfirmed complete consumption of the starting alcohol. The reactionmixture was transferred to a 500 mL single neck flask and concentratedin vacuum to give a tan semi-solid which solidified on cooling to roomtemperature. The crude product (82.10 g) was suspended in hot methanol(200 mL) and heated to dissolve the solid. The resulting solution wascooled to room temperature and on standing for 6 h, a significant amountof crystals were deposited.

The crystals were collected by suction filtration, rinsed with ice coldmethanol (2×25 mL) and dried in vacuum at room temperature for 18 h togive 28.03 g of material. The mother liquor was reduced to half itsoriginal volume and cooled in an ice bath to deposit additional solid.The second crystal crop was isolated as described above to give anadditional 6.81 g of material. The two crystal crops were combined andpurified by dry flash column chromatography using Flash grade silica gelusing 50% dichloromethane/50% hexane as eluant. The material was furtherpurified by recrystallization from hexanes. After drying at 50° C. for24 h, N-[(perfluorooctanesulfonyl)oxy]-5-norbornene-2,3-dicarboximidewas isolated as a white crystalline solid.

FORMULATION EXAMPLES Example 1

A control resist formulation comprising a terpolymer of4-hydroxystyrene, styrene and t-butylacrylate (72.35 g of a 20 wt. %solution in ethyl lactate), di-(4-t-butylphenyl)iodoniumcamphorsulfonate (DTBIOCS) 7.23 g of 10 wt. % solution in ethyllactate), a basic additive (2.89 g of 20 wt. % solution in propyleneglycol monomethyl ether acetate), copolymer of 9-anthracenemethacrylate, and 2-hydroxyethyl methacrylate (0.23 g), Silwet™ L-7604(1.60 g of a 5 wt. % solution in ethyl lactate) and ethyl lactate (15.69g) was prepared.

Examples 2 to 5

Formulation examples 2 to 8 were prepared in a similar fashion to thatdescribed above incorporating the formulation indicated in Table II.

RESIST PROCESSING EXAMPLES

Table 1 details the process conditions for the experiment using theresist formulation of the Formulation 1 Example. The wafers wereprocessed on a GCA Microtrak coater and developer equipped for contactbakes. Exposures were performed on a GCAXLS7800 0.53NA, 0.74σ DUVStepper.

TABLE I Process Information for Formulation DOE Process Variable SettingThickness 6570 Å (E_(min)) Softbake 135° C., 60 sec. PEB 125-145° C. in5° C. steps Developer MF-501 (0.24 N surf.) Develop Process 45 sec.Single stream puddle, 16 psi, Puddle Build 4 sec @ 500 rpm + 2 sec @ 50rpm

Results

Table II summarizes the PEB sensitivity results over the 130-140° C. fordyed resist formulations. PEB sensitivity is defined as the differenceis line width between the smallest and widest lines across the resistsurface.

TABLE II PEB Sensitivity Results over 130-140° C. PEB Range PEBSensitivity Example Formulation (nm/° C.) 1 Control (5% DTBPIOCS, 14.74% Polyethyoxylated ethylene diamine 2 5% DTBPIOCS 11.9 0.4% DTBPILactate 3 5% DTBPOTFMBS, 0.4% TBAH 4.0 4 5% DTBPIOPFOS, 0.4% TBAH 4.0 55% TPSCSA, 0.4% TBAH 9.3

The invention should not be construed as limited to the above recitedexamples.

What is claimed is:
 1. A positive working photoresist compositioncomprising an alkali soluble resin substituted with an acid labileblocking group that requires an activation energy of at least 20Kcal/mol for deblocking, and a photoacid generating compound thatundergoes photolysis when exposed to a pattern of activating radition ata wavelength of 350 nm or less to yield a sulfonic acid having a strongelectron withdrawing group and a pK_(a) that does not exceed 0, thephotoacid generating compound has a formula:

where R is an organic radical having from 1 to 18 carbon atoms, X is astrong electron withdrawing group, a is a whole number from 1 to 18, R⁷is a straight chain branched or cyclic alkyl group having from 1 to 10carbon atoms and Z is a sulfonyl or a carbonyl group, the alkali solubleresin binder conforms to the formula:

where x is from about 10 to 90 percent, y is from about 1 to 75 percent,and z is from 1 to 75 percent of the mole fraction, the hydroxyl groupon the hydroxystyrene may be present at either the ortho, meta, or parapositions throughout the copolymer, R¹¹ is substituted or unsubstitutedalkyl having 1 to 10 carbon atoms, R¹ and R² are independently halogen,substituted or unsubstituted alkyl having from 1 to 8 carbon atoms,substituted or unsubstituted alkoxy having from 1 to 8 carbon atoms,substituted or unsubstituted alkenyl having 2 to 8 carbon atoms,substituted or unsubstituted alkythio having from 1 to 8 carbon atoms,cyano, and nitro; and m is an integer of from 0 to 5 and p is an integerof from 0 to 4; and R³, R⁴, and R⁵ are hydrogen.
 2. The photoresist ofclaim 1 where the pK_(a) varies between −5 and −15.
 3. The photoresistof claim 1 where the strong electron withdrawing group is selected fromthe group consisting of halo, nitro, and cyano.
 4. The photoresist ofclaim 3 where the strong electron withdrawing group is fluoro.
 5. Thephotoresist of claim 1 where the strong electron withdrawing group isperfluoroalkyl having from 1 to 18 carbon atoms.
 6. The photoresist ofclaim 5 where the strong electron withdrawing group is trifluoromethyl.7. The photoresist of claim 1 where the acid labile blocking grouprequires an activation energy of from about 25 to 40 Kcal/mol fordeblocking.
 8. The photoresist of claim 1 where the acid labile group isan acetate group.
 9. The photoresist of claim 1 containing a base havinga pK_(a) of at least
 9. 10. The photoresist of claim 9 where the pK_(a)varies between 11 and
 15. 11. The photoresist of claim 1 furthercomprising a base having a formula N(R′)₄A where R′ is substituted orunsubstituted alkyl or substituted or unsubstituted aryl, A is a counteranion of a member selected from the group consisting of halide, asubstituted or unsubstituted hydroxyalkanoyl having from 1 to 18 carbonatoms and substituted or unsubstituted sulfonate.
 12. The photoresist ofclaim 11 where the counter anion is sulfonate.
 13. The photoresist ofclaim 11 where the counter anion is selected from the group consistingof mesylate, triflate and tosylate.
 14. The positive working photoresistcomposition of claim 1, wherein x is from about 20 to 90 percent of themole fraction.
 15. The positive working photoresist composition of claim1, wherein y is from about 2 to 60 percent of the mole fraction.
 16. Thepositive working photoresist composition of claim 1, wherein z is fromabout 2 to 60 percent of the mole fraction.
 17. A positive workingphotoresist composition comprising an alkali soluble resin substitutedwith an acid labile blocking group that requires an activation energy ofat least 20 Kcal/mol for deblocking, and a photoacid generating compoundthat undergoes photolysis when exposed to a pattern of activatingradition at a wavelength of 350 nm or less to yield a sulfonic acidhaving a strong electron withdrawing group and a pK_(a) that does notexceed 0, the sulfonic acid is selected from the group consisting ofperfluorooctane sulfonic acid and 2-trifluoromethylbenzene sulfonicacid, the alkali soluble resin binder conforms to the formula:

where x is from about 10 to 90 percent, y is from about 1 to 75 percent,and z is from 1 to 75 percent of the mole fraction, the hydroxyl groupon the hydroxystyrene may be present at either the ortho, meta, or parapositions throughout the copolymer, R¹¹ is substituted or unsubstitutedalkyl having 1 to 10 carbon atoms, R¹ and R² are independently halogen,substituted or unsubstituted alkyl having from 1 to 8 carbon atoms,substituted or unsubstituted alkoxy having from 1 to 8 carbon atoms,substituted or unsubstituted alkenyl having 2 to 8 carbon atoms,substituted or unsubstituted alkythio having from 1 to 8 carbon atoms,cyano, and nitro; and m is an integer of from 0 to 5 and p is an integerof from 0 to 4; and R³, R⁴, and R⁵ are hydrogen.